Trump could bridge the divide between the elites and GOP voters. Instead, he’s deepening it.

As tribune of the base Donald Trump is successful and inadequate. You see it in the Muslim question. His strength is that he responds to and appears to share the concerns of those who are legitimately worried about whom we allow into the United States—our visa protocols, our vetting, our standards. This is a national-security issue. We have entered the age of ISIS-inspired and ISIS-directed attacks on the West. The latter (Paris) have tended to be bloodier than the former (San Bernardino), because they involve more operatives, more simultaneous targets, more weapons. Whether inspired or directed, the idea of future hits...